Coiled wire element



June 2, 1970 W. R. JONES COILED WIRE ELEMENT Filed April 1, 1969 INVENTOR WILLIAM R. JONES United States Patent Oflice 3,515,241 Patented June 2, 1970 ABSTRACT OF THE DISCLOSURE A continuous wire element of helical configuration the helix being formed by a plurality of essentially circular interconnected loops, each loop contacting the two adjacent loops and the centers of each loop being offset in opposite directions with respect to the centers of the next adjacent loops. In a typical application the element housed in a suitable casing constitutes a silencer for a pump, compressor or other air handling apparatus or a muffler and spark arrestor for an internal combustion engine.

BACKGROUND OF THE INVENTION In recent years the use of relatively small gasoline engines has increased enormously. A substantial portion of the increase in this use is attributable to the application of such engines to units such as power mowers, chain saws, portable power plants, motor bikes and the like which are operated in residential communities. Accordingly, considerable attention has been devoted to the problem of affecting adequate mufifing of such engines to abate the annoying noise and to reduce or eliminate fire hazards which may result from inadequate muffling. While mufllers are available having the desired sound reduction and spark arresting characteristics such mufflers generally are too expensive or too bulky to permit the use on small engines. =Often such mufllers create flow restrictions in the exhaust or intake line which materially affects engine performance. Accordingly, mufllers of rudimentary construction have continued in widespread use. Such mufilers generally provide inadequate sound reduction and are subject to relatively rapid deterioration.

SUMMARY OF THE INVENTION It is the principal purpose and object of the present invention to provide improved gas flow control devices such as mufilers for internal combustion engines, and silencers for pumps, compressors and the like, which provide improved sound control and spark arresting performance, which are of inexpensive compact construction, and which minimize flow restriction in the exhaust or intake line in which they are installed.

To this end the present invention provides a muffler comprising an imperforate casing open at both ends and a filler for the casing, the filler comprising a continuous length of wire formed into a plurality of connected essentially circular loops, each loop preferably lying in partial surface contact with the next adjacent loops and the centers of each loop being offset with respect to the next adjacent loops to form a helix.

The mass of wire comprising the filter core presents an unusually large surface area against which the gasses impinge.

Sparks, which are small particles of red hot carbon, cannot pass through the filter without striking one or more lengths of wire. Accordingly, the particles ricochet through the filter, the ricocheting action tending to break up and cool the particles which then pass out of the muffler in harmless condition.

Similarly when the unit is used as a muffler on a compressor it substantially reduces the possibility of ice formation within the mufller and causes particles of ice which may form to break up and pass out of the mufiler before they can accumulate and create substantial flow restriction.

Additional objects and advantages will become apparent as the description proceeds.

THE DRAWINGS FIG. 1 is a central section through a mufiler constructed in accordance with the present invention.

FIG. 2 is a transverse section along line 22 of FIG. 1;

FIG. 3 is an enlarged fragmentary view of the wire element; and

FIG. 4 is a side'view of the wire element showing a portion as it appears when unwound from its normal helical form.

DESCRIPTION OF PREFERRED EMBODIMENT While the wire element of the present invention may be advantageously utilized in a 'variety of environments, for present purposes it will be described in combination with associated structure forming a muffler especially adapted for installation on a relatively small (i.e., /2 to 5 horsepower) air cooled gasoline engine.

The mufiler comprises a relatively thin wall casing 20 of sheet metal of generally cylindrical form. The casing preferably comprises a pair of tubular members 22 and 24, the latter being partially telescoped over the former. After assembly, the casing parts are tack-welded. The casing part 24 has a reduced end portion 26 externally threaded for attachment to a boss 28 surrounding the exhaust port 30 of the engine, not shown. The casing part 22 also has a reduced end portion 32 having a central opening 34 providing the exhaust gas outlet.

The casing 20, which is essentially of conventional construction, is usually provided with a number of transverse sheet metal bafile walls to create a tortuous path through the casing. Such bafiles, however, have little silencing effect and they may become resonators which pass sound energy directly to the casing to which they are rigidly attached.

In accordance with the present invention the rigid casingamounted bafiles are replaced by a wire baflfe element indicated generally at 36 which is loosely confined in the casing.

The element 36 is related to the spring disclosed in copending application Ser. No. 711,774 filed March 1968 for Springs and owned by applicants assignee. As in the application the element comprises a number of interconnected coils or loops 38 of identical configuration. Adjacent coils are interconnected by bridge portions one of which is shown at 40. Whereas in the spring disclosed in the aforesaid application the planes of the coils are disposed at a substantial angle with respect to the central axis of the spring, the plaries of the coils 38 are essentially normal to the longitudinal axis of the element and each coil is in partial surface contact with the next adjacent coil.

To form the helical element shown in FIG. 1 the longitudinal axis 37 is curved in the plane of FIG. 4 to essentially circular form. As this is done the individual loops are displaced in a direction normal to the plane of FIG. 4 to form the helix. It will be appreciated that the element is formed to its final helical configuration shown in FIG. 1 in a single step in an automatic wire cooling apparatus.

After the wire element has been formed to its helical configuration it is fitted loosely into the casing part 24. The casing part 22 is then assembled to the part 24 and the parts are tack-welded together. Preferably the external diameter of the helix formed by the wire element is essentially the same as the internal diameter of the cas- 3 ing parts 22 and 24 and the length of the wire element, when relaxed, is somewhat greater than the corresponding dimension of the mufller casing so that the wire element is installed in the casing under light axial compresslon.

In a typical case the diameter of the muffler casing 20 is an inch and a half and its length is approximately three inches. The diameter of the individual loops 38 is approximately five-eighths of an inch and there are from 30-40 such loops per linear inch. Accordingly the total length of the wire within the mufiler casing is over two hundred inches thus providing the unusually large surface area which is effective to provide attenuation of the engine noise, elimination of sparks, and, where the unit is installed on a compressor, effectve control of the formation of ice particles.

It will be understood that by varying the ratio between the diameter of the individual loops 38 and the diameter of the helix into which they are formed the diameter of the open core of the helix can be varied or the open core may be eliminated.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive.

What is claimed and desired to be secured by Letters Patent is:

1. A gas flow control device comprising tubular casing structure having opposed end walls, one of said walls being provided with an inlet opening and the opposite wall being provided with an outlet opening, and a continuous length of wire within said casing structure and extending between said opposed walls, said length of wire being formed into a series of interconnected essentially identical generally circular loops, each loop being in partial surface contact with the next adjacent loops and the center of each loop being olfset from the centers of the adjacent loops in a manner to form a helix.

2. A gas flow control device as defined in claim 1 in which the external diameter of the helix is essentially the same as the internal diameter of the casing structure and the diameter of each loop is substantially smaller than the internal diameter of the casing structure.

References Cited UNITED STATES PATENTS 428,868 5/ 1890 Stoakes et a1 267-74 XR 714,128 11/1902 Barber 181-49 1,376,263 4/ 1921 Emerson 181-60 XR 2,001,835 5/1935 Cook 267-167 3,205,468 9/1965 Henschen 267180 XR 3,227,242 1/ 1966 Mattoon 181-61 3,276,761 10/1966 Becker 267-167 FOREIGN PATENTS 808,437 11/1936 France. 303,581 1/1929 Great Britain. 471,431 9/1937 Great Britain. 563,110 7/1944 Great Britain. 556,847 2/1957 Italy.

ROBERT S. WARD, 1a., Primary Examiner US. Cl. X.R. 181--58, 67 

